1. Field of the Invention
The present invention relates generally to the field of wireless communications and devices, and more particularly to the design of antennas configured for robust multiple band multi-input multi-output (MIMO) implementations for use in wireless communications.
2. Description of the Related Art
Commonly owned U.S. Pat. Nos. 7,339,531; 6,943,730; 6,919,857; 6,900,773; 6,859,175; 6,744,410; 6,323,810; and 6,515,634; describe an IMD antenna formed by coupling one element to another in a manner that forms a capacitively loaded inductive loop, setting up a magnetic dipole mode; the entire disclosures of which are hereby incorporated by reference. The magnetic dipole mode can also be generated by inducing a current mode onto a conductive element with specific slot geometry. This magnetic dipole mode provides a single or dual resonance and forms an antenna that is efficient and well isolated from the surrounding structure. This is, in effect, a self resonant structure that is de-coupled from the local environment. This antenna typically has a single feed for connection of the antenna to the transceiver. The IMD antenna is well isolated from the surrounding environment and two or more IMD antennas can be closely spaced and maintain high levels of isolation. This high isolation is a desired attribute for antennas directed toward multi-input multi-output (MIMO) implementations.
Current and future communication systems will require MIMO antenna systems capable of operation over multiple frequency bands. Isolation between adjacent elements as well as de-correlated radiation patterns will need to be maintained across multiple frequency bands, with antenna efficiency needing to be optimized for the antenna system.